Author
Topic: Chain Skipping on MTB (Read 1550 times)

I have an old (~2007) Genesis Core 30 hardtail which has recently started to suffer from really bad chain skipping every time I put it under load. It seems independent of which gear it's in (it's an old 3 x 9 format). Most of the gear is Deore.

I've looked around on Google and narrowed it down to the chain, or the cassette , the chainrings or maybe the hub. i.e. just about anything. The rear mech also looks a little twisted and the jockey wheels are very worn, with a couple almost completely missing. I can't adjust the L screw enough to stop it crashing into the spokes so it probably needs replacing anyway.

I've replaced the chain and it made no difference, does anybody have any suggestions ?

I'm a bit reluctant to start throwing parts at it, especially if I end up replacing the entire drivetrain. Rather than doing this I'd rather just upgrade it to either 3x10 or maybe 1x11, as the only additional expense as I see it would be the shifters.

Any suggestions anyone ? If I end up swapping parts out, then I'd like to do it in a way that, if possible, I end up with an upgraded bike (for instance can I swap the rear mech for a 10 speed mech ? Will it work on a 9 speed cassette with 9 speed shifters ?

Since posting that, I've just swapped out the cassette with another 9 speed from a road bike and it's made no difference, it's still skipping. Next step is to swap the derailleur from the same bike (a fairly recent Ultegra) and see what difference it makes.

I know that I'd end up changing everything if I do go 10 speed, but figured if I'm going to have to change most of it anyway, then I'd rather end up with a 10 speed than a 9 speed. I'm just not sure if the 10 speed mech will work in a 9 speed configuration in the meantime.

I swapped the Ultegra mech onto the Core and low and behold. It still skipped. However I also noticed that it didn't look aligned either, so I took out the hanger and when I laid it on a flat surface it was slightly bent.

I straightened it as best I could in a vice, but couldn't get it perfect, however even at that when I retried it, it didn't skip.

This is with the Ultegra mech and the 9 speed cassette off a road bike.

Next stage is to get a new hanger and see how it works. I can then swap everything back and make a call whether to upgrade it to a 10 speed or not.

I swapped the Ultegra mech onto the Core and low and behold. It still skipped. However I also noticed that it didn't look aligned either, so I took out the hanger and when I laid it on a flat surface it was slightly bent.

I straightened it as best I could in a vice, but couldn't get it perfect, however even at that when I retried it, it didn't skip.

This is with the Ultegra mech and the 9 speed cassette off a road bike.

Next stage is to get a new hanger and see how it works. I can then swap everything back and make a call whether to upgrade it to a 10 speed or not.

Thanks all so far.

The one essential tool every rider, road or MTB, should have is a hanger alignment tool!!! If you don't start by making sure the hanger is spot on you end up wasting time fiddling to get the gears kind of working!

Once the hanger is straight move the mech by hand with no cable or chain attached and set the High and Low limit screws, reconnect the cable with the shifter in smallest sprocket, then unscrew the cable adjuster to take out all the slack and to the point where the mech just starts to move, back the adjuster off a quarter turn.

Replace the chain and then finally check the adjustment of the B screw to get the recommended gap between the cassette and jockey wheel (make sure to do it in the correct gear, Sram sell a plastic guage for their 1 X systems.

Finally enjoy lovely gear selection!!!

It is most obvious if the cable needs adjusting if the first shift from smallest sprocket to its neighbour isn't 100% reliable then unscrew the adjuster a half turn at a time until that change is spot on, the rest usually fall into place.